A power failure or a temporary drop in power-supply voltage often causes not only an interruption of operations of electronic devices in use, but also a more significant problem such as the corruption of stored data and mechanical failures.
Therefore, Japanese Unexamined Patent Application Publication No. 2006-271074 (Patent literature 1) “UNINTERRUPTIBLE POWER SUPPLY SYSTEM” proposes an uninterruptible power supply apparatus equipped with a secondary battery (battery) and thereby capable of continuing the supply of electric power even when a temporary power failure occurs. Further, the secondary battery mounted in the apparatus needs to be kept in a charged state. Further, since the secondary battery deteriorates with time, it is necessary to measure the degree of the deterioration as required and to replace it with new one at regular intervals. Japanese Unexamined Patent Application Publication No. 2000-121710 (Patent literature 2) “BATTERY CONTROL DEVICE FOR BACKUP POWER SUPPLY AND METHOD FOR DIAGNOSING DETERIORATION OF SECONDARY BATTERY” proposes a secondary battery deterioration measurement technique that makes it possible to estimate the degree of deterioration of a secondary battery by causing a pulse discharge with a constant current and measuring the battery voltage before and during the discharge.